Male Reproductive Anatomy of Cattle

1. Male Reproductive Anatomy of Cattle By C. Kohn, Waterford WI

4. The Male Reproductive Tract - Overview • The reproductive tract of a bull has two parts – • 1. The testicles, including • Seminiferous Tubules made of Leydig Cells and Sertoli Cells • 2. The secondary sex organs, including… • Epididymis • Vas Deferens • Seminal Vesicle • Prostate Gland • Cowper’s Gland • Urethra and Penis

5. The Testicles • The testicles have two functions: • 1. Production of the spermatozoa that will become the sperm cells • 2. Production of testosterone, the ‘male’ hormone • The testicle is the entire organ, consisting of the testis (plural: testes), the scrotum (outer covering of skin), and beginning of the epididymis

6. Seminiferous tubules & Sertoli Cells • Each testis is comprised of long, coiling structures called Seminiferous Tubules • Each seminiferous tubule is comprised of connected Sertoli cells • The Sertoli cells are what produce and nurture developing sperm

8. Blood Testis Barrier • Sertoli cells have a “tight junction” barrier which serves to prevent the body from destroying the sperm. • Why would the body destroy sperm? • HINT: Chromosome #’s and types • The BTB is a physical barrier between the testes and the seminiferous tubules. • Think of the grapefruit! ~

9. BTB • The Sertoli cells form a barrier that prevents blood from accessing the lumen of the seminferous tubules. • How is this a good thing? • How is this a bad thing? • What would happen if the BTB were breached? • TPS~

10. Leydig Cells • Leydig cells/interstitial cells are dispersed throughout the testes and produce male hormones (androgens) • Testosterone is considered the primary male hormone • Testosterone is released under the influence of LH from the pituitary gland. • Both LH and FSH are needed for sperm production ~

11. Male Hormones • Male Hormones are necessary for: • Onset and maintenance of sperm production • Sex drive (libido) • Development and maintenance of secondary sex characteristics (organs and features) ~ • After puberty, spermatozoa formation is a continuous process. • This process is controlled by the endocrine system. • FSH and LH are important in stimulating the testes to produce spermatozoa and testosterone. ~

12. Male Hormone Loop • Brain releases GnRH, which tells pituitary to release FSH, LH • LH tells Leydig cells to release testosterone, whichstimulates production of sperm.- note negative feedback! • Testosterone also slows the release of LH (as does Inhibin for FSH) • What would injections of testosterone due to sperm production?

13. Male Hormone Cycle • 1. Brain releases GnRH • 2. GnRH causes release of LH, FSH • 3. LH causes release of testosterone from Leydig Cells • 4. Testosterone causes production of sperm in Sertoli Cells (as well as production of Inhibin) • 5. Testosterone reduces production of LH; Inhibin reduces production of FSH

14. Temperature Control • The testicles must located outside of the male’s body as normal sperm formation occurs at a temperature several degrees below normal body temperature • Very cold temperatures can also damage the scrotum. • To keep the testicles at the proper temperature, the cremaster muscle suspends or retracts to move the testicles closer to or further from the body • Testosterone causes this response; no testosterone, no cremaster function • This muscle can be damaged or other injury or malformation can prevent one or both testicles from descending. This condition is called cryptorchidism • An individual with this condition will be partially or fully sterile and this individual should not be allowed to breed.

15. Causes of sterility • Conditions other than cryptorchidism can also cause sterility in males, including • - excessive fat deposits in the scrotum • - a very high fever or high fever over several days • - very hot weather for an extended period of time • If the male was producing sperm prior to these occurrences, sperm production may resume after 6-10 weeks.

16. Epididymus • After leaving the testes through ducts in the seminiferous tubules, sperm enter the epididymus. • The epididymus is a tubular structure located on one side of the testes. • It is packed with a milky nutritive substance as well as spermatozoa from the testes. • Spermatozoa mature in the epididymus • An assembly line, not a storage unit!~

17. Vas Deferens • From the epididymus, spermatozoa enter the vas deferens. • This carries the spermatozoa into the body cavity towards the urethra • It is surrounded by muscles that contract during ejaculation. ~

18. Ampullae of Henle, Urethra • The vas deferens enlarges inside the pelvis to form the ampullae • Where spermatozoa are stored and mixed with a nutritive substance. • During copulation, sperm is moved into the urethra. • This is a common pathway for both urine and semen (the mix of the products of the testes and accessory glands.) ~

19. Urethra

20. Accessory Glands (3) • There are three accessory glands: • 1. Seminal Vesicles – secrete a fluid high in sugars (fructose) to nourish the spermatozoa – feels like a bag of grapes (palpation) • This fluid also dilutes sperm at ejaculation and serves to activate motility – the bulk of fluid production occurs here • Rich in proteins, fructose, enzymes. • Secretes prostaglandins, causing uterine contractions • 2. Prostate glands – Creates a basic pH of 7.5-8 – protects sperm • 3. Cowper’s gland – lubricating & cleansingsubstance • Cleanse male and female reproductive tracts prior to passage of spermatozoa (King Sperm’s archers) • These secretions are released almost instantaneously • Yellowed cloudy semen secretions may indicated an infection in these glands

22. Urethra and Penis • The urethra extends to the tip of the penis, where it exits the body. • Urethra surrounded by smooth muscle – crucial for ejaculation. • Penis is composed of sponge-like blood tissue • Under sexual stimulation, this tissue fills with blood, enlarging it and enabling it to be inserted into a female’s vagina. • Otherwise, it is kept inside the body cavity in most species ~

24. Briefly – EDC’s • Endocrine Disrupting Chemicals are a serious concern today. • These chemicals have similar chemical conformations to sex hormones and mimic their effects in the body. • What impact would this have on a body; remember negative feedback! ~

25. EDC’s • “To date, in vitro and in vivo studies have identified several antiandrogenic toxicants including vinclozolin, procymidone, linuron, several phthalate esters, and p,p’-DDE, all of which alter male rat sex differentiation.” • Emerging Issues Related to Endocrine Disrupting Chemicals and Environmental Androgens and Antiandrogens • Gray, et. al. , US Environmental Protection Agency ~

26. A Concern • In humans and other mammals, male fertility has dropped significantly. • This has also been seen in cattle; it is much harder to breed a cow today than it was 50 years ago. • Furthermore, cases of sexual abnormalities have increased in amphibians and reptiles. • Is this genetic or environmental? ~

27. Sperm Situations • Sperm are not hardy; they are rather fragile cells • They are very susceptible to: • Heat • Jarring • Radiation • Poor Nutrition • Infrequent ejaculation (increases abnormalities) • A mature bull can ejaculate as much as 7 consecutive times without a severe reduction in spermatozoa

28. Infertility • Infertility is not immediately recognizable! • Symptoms may show 2.5-3 mo’s after! • It takes ~70 days to produce sperm, and over two weeks to travel through the epididymus. • A mature bull should produce 70 billion sperm/week. • The heavier the testes, the more sperm is produced.